1. Field of the Invention
The present invention relates to circuit boards, and more particularly, to a circuit board on which an electronic component is to be mounted.
2. Description of the Related Art
Circuit boards including laminates of ceramic layers are known as conventional general circuit boards. FIG. 10 is a diagram illustrating a conventional circuit board 500 mounted on a printed wiring board 600. In addition, an electronic component 700 is mounted on the circuit board 500.
As illustrated in FIG. 10, the circuit board 500 is composed of a main body 501 and external electrodes 502 and 503. The main body 501 is composed of a laminate of ceramic layers and is a rigid board. The external electrodes 502 and 503 are provided on a top surface and a bottom surface, respectively, of the main body 501.
The printed wiring board 600 is a motherboard mounted on, for example, an electronic device, such as a mobile phone, and is provided with a main body 601 and external electrodes 602, as illustrated in FIG. 10. The main board is a rigid board made of resin or the like. The external electrodes 602 are provided on a top surface of the main body 601.
The electronic component 700 is, for example, a semiconductor integrated circuit and is provided with a main body 701 and external electrodes 702. The main body 701 is a semiconductor board. The external electrodes 702 are provided on the bottom surface of the main body 701.
As illustrated in FIG. 10, the circuit board 500 is mounted on the printed wiring board 600. Specifically, the circuit board 500 is mounted by connecting the external electrodes 502 to the external electrodes 602 by solder.
As illustrated in FIG. 10, the electronic component 700 is mounted on the circuit board 500. Specifically, the electronic component 700 is mounted by connecting the external electrodes 503 to the external electrodes 702 by solder. The circuit board 500, the printed wiring board 600, and the electronic component 700 described above are to be mounted in an electronic device, such as a mobile phone.
Meanwhile, the conventional circuit board 500 has a problem in that it is likely to be detached from the printed wiring board 600. More specifically, it is likely that the printed wiring board 600 is bent by shock generated when the electronic component containing the circuit board 500 and the printed wiring board 600 is dropped. Even if the printed wiring board 600 is bent, the circuit board 500 may not be bent significantly along with the bending of the printed wiring board 600 since the circuit board 500 is a rigid board. Thus, stress is imposed on the solder connecting the external electrodes 502 to the external electrodes 602. As a result, the solder is broken, and the circuit board 500 is detached from the printed wiring board 600.
To overcome the above problem, the circuit board 500 may be fabricated by laminating sheets made of a flexible material. A printed circuit board disclosed in Japanese Unexamined Patent Application Publication No. 2006-93438, for example, includes a laminate of sheets made of a flexible material. FIG. 10 is used as a reference of a configuration of a printed board 800.
The printed board 800 disclosed in Japanese Unexamined Patent Application Publication No. 2006-93438 includes a main body 801 and external electrodes (lands) 802 and 803. The main body 801 is composed of a laminate of sheets made of thermoplastic resin. The external electrodes 802 and 803 are provided on the top surface and the bottom surface, respectively, of the main body 801. Similarly to the circuit board 500, the printed board 800 is mounted on the printed wiring board 600 through the external electrodes 802 on the bottom surface. Similarly to the circuit board 500, the electronic component 700 is mounted on the printed board 800 through the external electrodes 803 on the top surface.
However, in the printed board 800 disclosed in Japanese Unexamined Patent Application Publication No. 2006-93438, the electronic component 700 is likely to be detached. Specifically, the printed board 800 can be bent since it is composed of sheets made of a flexible material. Thus, if the printed wiring board 600 is bent, the printed board 800 can be bent along with the bending of the printed wiring board 600. Thus, it is possible to prevent the printed board 800 from being detached from the printed wiring board 600 due to breakage of solder connecting the external electrodes 602 and the external electrodes 802.
Meanwhile, the printed board 800 has flexibility over its entire surface, and thus, the entire surface of the printed board 800 can be bent. On the other hand, the electronic component 700 is composed of a semiconductor board and, thus, cannot be bent significantly. Thus, stress is imposed on the external electrodes 702 and 803 and the solder connecting the external electrodes 702 and 803. As a result, the solder may be broken, and the external electrodes 702 and 803 may be detached from the main bodies 701 and 801. That is, the electronic component 700 and the printed board 800 may be disconnected.
In FIG. 10, the printed board 800 is attached to the printed wiring board 600 through the external electrodes 802. However, in a case in which the printed board 800 is attached to a casing by an adhesive or other material, the problem of possible disconnection between the electronic component 700 and the printed board 800 may also occur.